Comparison of percutaneous cystolithotomy and open cystotomy for removal of urethral and bladder uroliths in dogs: Retrospective study of 81 cases (2014‐2018)

Abstract Objective Compare percutaneous cystolithotomy (PCCL) and open cystotomy (OC) for removal of bladder and urethral uroliths. Design Retrospective study. Animals Client‐owned dogs and cats that underwent PCCL (n = 41) or OC (n = 40) between January 1, 2014 and February 28, 2018 at a referral center. Methods Medical records of dogs and cats that underwent a PCCL or an OC were reviewed. History, signalment, physical examination, diagnostic tests, length of the procedure and anesthesia, complications, and duration of hospitalization were recorded. Results A total 17 cats (PCCL = 10; OC = 7) and 64 dogs (PCCL = 31; OC = 33) were included. There was no significant difference, regardless of species, in the mean surgical time (45 min [24‐160 min] and 48.5 min [15‐122 min] with P = .54 in dogs, P = .65 in cats) nor mean duration of anesthesia (90 min [50‐120 min] and 98 min [54‐223 min] with P = .87 in dogs, P = .08 in cats) in the PCCL and OC groups respectively. Number of uroliths did not affect duration of surgery in either group. Complete urolith removal was achieved in 98% of dogs and cats in both groups. The median hospitalization time was significantly shorter in the PCCL group for dogs (11.3 hours [range 4 to 51.3] in the PCCL vs 56.6 hours [range 7.3 to 96] in the OC group; P < .001) but did not differ for cats (24.5 hours [range 8.3 to 30] in the PCCL vs 56.6 hours [range 10.1 to 193.2] in the OC group; P = .08). Conclusion and Clinical Relevance Bladder urolith removal by PCCL procedure is no longer than OC. Further studies are needed to compare the pain related to procedure between PCCL and OC.

The objective of this study was to compare surgical technique, perioperative and postoperative complications, anesthesia time, surgery time, and length of hospitalization in dogs and cats undergoing PCCL or OC. We hypothesized that length of surgery and anesthesia would be similar for PCCL and OC with similar complication rates however that length of postoperative hospitalization would be significantly shorter in the PCCL group.

| Case selection
Medical records of all client-owned cats and dogs that had undergone PCCL or OC for removal of bladder, urethral or both uroliths from the DMV Center between January 6, 2014 and February 28, 2018 were reviewed. Dogs and cats of any age, sex, and size and with any number of bladder or urethral uroliths were included if a PCCL procedure or OC had been performed.
Dogs and cats were included if a complete medical record was available for review, including a 2 week postoperative examination.
Signalment, medical history, laboratory (complete blood count, serum biochemistry, and urinalysis) and imaging results and number and type of uroliths were recorded. Length of anesthesia and surgery, number and type of uroliths removed, peri and short-term postoperative complications (0-14 days after the procedure) and duration of hospitalization were recorded. Animals were excluded if the medical records were incomplete or if the 2 week postoperative examination was unavailable. All procedures performed without a board-certified surgeon were excluded.  ately sized red rubber urethral catheter was placed in a retrograde manner. Sterile saline was infused until the bladder apex could be palpated and a PCCL procedure was performed as previously described. 10 Briefly, a 1 cm ventral midline skin incision was performed. Two stay sutures were placed in the right and the left external rectus sheath to retract the body wall with 2-0 polydioxanone (PDS suture, Ethicon Inc, Somerville, New Jersey, USA). The bladder apex was retracted cranially and a third stay suture was placed at the bladder apex with 3-0 polydioxanone suture. Two more stay sutures were placed on the right and on the left side of the ventral aspect of the apex of the bladder. A stab incision with #15 or #11 scalpel blade was made into the bladder lumen. Bloomington, Indiana, USA) was used to grasp the uroliths and remove them through the trocar. Uroliths larger than the 5-mm inner diameter of the trocar were entrapped in the urolith basket. The trocar and uroliths were removed from the bladder. Once the procedure was complete, the urethra was inspected with a flexible ureteroscope.

| PCCL procedure
As the cystoscope was directed down the urethral lumen, the red rubber catheter was withdrawn and irrigation performed with saline allowing retrograde flush of any remaining urolith fragments. If uroliths were identified, they were retrieved by use of a urolith basket.
The ureteroscope was advanced as far down the urethra as possible for male cats and to the proximal aspect of the os penis in small dogs.
The bladder incision was closed in 1 or 2 layers at the surgeon's discretion: a simple continuous suture pattern and a Cushing pattern or 2 cruciates sutures with 3-0 (dogs) or 4-0 (cats) polydioxanone or poliglecaprone 25 sutures (Monocryl suture, Ethicon Inc, Somerville, New Jersey, USA). The abdominal incision was closed routinely in 3 layers.
One non absorbable nylon cruciate suture (Ethilon suture, Ethicon Inc, Somerville, NJ) or surgical glue was used to close the skin incision.
A nonadherent dressing (Opsite, Smith&Nephew Medical Ltd, Hull, England) was placed for the duration of the hospital stay.

| Cystotomy procedure
The procedure was performed by a board-certified surgeon (MG, JP, JB) and surgical interns. Dog or cat was placed in dorsal recumbency after a standard aseptic preparation of the abdomen. Sterile saline was infused through the red rubber catheter placed as described in the PCCL procedure section. The OC was routinely performed as previously described. 2 The skin incision length varied from 2 to 7 cm depending on the size of the dog or the cat. The bladder and abdominal incisions were closed as described for the PCCL procedure. An adhesive dressing was placed for the duration of the hospital stay.

| Complications
Intraoperative complications were defined as complications noted during the surgical procedure. They were classified as severe or minor.
Severe complications were defined as complications which could be life-threatening or which needed surgical conversion from PCCL to OC. Minor complications were associated with an increased surgical time that did not require surgical conversion from PCCL to OC.

| Postoperative management
All dogs and cats with radio-opaque uroliths had a lateral and ventrodorsal abdominal radiographs taken immediately after surgery to confirm urolith removal defined as no uroliths in the bladder nor urethra directly visualized during the PCCL procedure and on postoperative abdominal radiographs (when applicable). For the OC procedure, complete urolith removal was characterized by absence of uroliths on postoperative abdominal radiographs (when applicable). If uroliths were seen within the urinary tract, a revision surgery was performed.

| Statistical analysis
Numeric values are summarized as mean ± SD. Unpaired Student's ttest was used to compare the length of anesthesia, length of surgery, the age and weight between the 2 groups (OC and PCCL).
Homogeneity of variance was tested with an F test. Welch's unpaired t-test was used to compare the hospitalization times between the 2 groups because of the disparity in variances (heteroscedasticity).
One-way ANOVA with Welch's correction was used to determine whether there were any statistically significant differences between

| Preoperative data
Abdominal radiographs were performed in 90.0% of dogs and cats

| Complications
There were no major intraoperative complications in the PCCL group, with no need for conversion to an OC. Postoperative abdominal radiographs were performed in both groups for all dogs and cats with radio opaque uroliths, which was the vast majority of animals (24 dogs and  In our study, complete urolith removal was achieved in 97.6% (40/41) of dogs (40) and cats (10) in the PCCL group. This is similar to a previous study, in which there was 1/27 dogs (3.7%) with incomplete urolith removal by PCCL. 1,7 In LAC, incomplete urolith removal was described in 3/50 dogs (6%). 12 In our study, there was 1 dog with cystine urolith fragments left intentionally in the bladder following PCCL, as their removal would have resulted in a prolonged procedural time. Given the small size of the fragments (<1 mm) it was expected that they would be evacuated from the bladder/dissolve following resolution of androgen dependent cystine crystalluria. No urolith recurrence was documented throughout the 2 year follow-up. The rate of persistence of small urolith fragments in the OC group remains uncertain as they are unlikely to be seen nor palpated during surgery.
In the OC group, 1 cat presented an obstruction 48 hours postoperatively due to a urethral urolith missed on postoperative radiographs.
Our results compare favorably to other studies that have reported urolith persistence rates after OC of 14% to 20% in dogs and up to 20% in cats. 2,5 The true persistence rate could have been underestimated in the OC group because of the lack of cystoscopic evaluation of the urinary tract at the end of the procedure, especially for small fragments typically not visible on radiographs. Though this could falsely decrease the percentage of incomplete uroliths removed in the OC group, these small fragments are unlikely to have clinical significance.
One dog had a free abdominal urolith after the OC procedure.
This minor complication was avoided in the PCCL group likely because of the pexy of the bladder to the abdominal wall limiting peritoneal cavity leakage during the procedure.
PCCL allows direct visualization of the lower urinary tract and image-guided urolith removal. Saline distension during PCCL combined with the magnification of the camera, allows better inspection of the bladder and urethral lumen. In particular, bladder biopsies can be easily performed with little added surgical time. 1,2,5,7 In this study, the surgical team did not consider it necessary to convert any PCCL procedure into OC. 1,10  This study has some limitations related its retrospective nature.
All the PCCLs were performed by the same internist in combination with the same surgeon for 93% of cases, limiting the bias associated with the change in operators. In the OC group, the 3 surgeons performed an equal number of OC, however surgical interns were involved in some of these surgeries which was not always specified in the medical files. Despite being under the direct supervision of a board-certified surgeon, the surgical and anesthetic times might have been increased in the OC group. Small sample size, especially in cats, might have led to decreased statistical power, which could explain the lack of a significant difference in hospitalization times between the 2 groups for cats (type II error). Hospitalization time has to be carefully interpreted as the perception that PCCL is a day procedure and Finally, the cost of equipment for the PCCL procedure and the time required to prepare and clean the operating room might be a limiting factor for some institutions.
In our study, length of surgery and anesthesia were not significantly different for PCCL and OC and hospital stays were significantly shorter in the PCCL group for dogs. We believe that PCCL can be safely and efficiently performed in dogs and cats regardless of weight, sex and with any number of uroliths. Complete urolith removal was achieved in 97.2% of dogs and cats by PCCL. Prospective randomized clinical trials to compare postoperative comfort and urolith recurrence rates between PCCL and OC are needed to better elucidate other potential benefits of PCCL over OC.

ACKNOWLEDGMENT
No funding was received for this study.